\begin{table}%t1
\caption {Critical values of $\chi^2$ for 3 probability levels.
\label{Table_Crit}}
%\centering
\par
\begin{tabular}{c c c c }
\hline\hline
\noalign{\smallskip}
%%\backslashbox{$n_i -\nu$}{$P_0$} & 0.05 & 0.1 & 0.2\\
$n_i -\nu$ & $\chi^2_{\rm crit} (P_0=0.05)$ & 
$\chi^2_{\rm crit} (P_0=0.1)$ & $\chi^2_{\rm crit} (P_0=0.2)$ \\
\hline
\noalign{\smallskip}
1 & 3.841 & 2.706 & 1.642 \\
2 & 5.991 & 4.605 & 3.219 \\
3 & 7.815 & 6.251 & 4.642 \\
4 & 9.488 & 7.779 & 5.989 \\
5 & 11.070 & 9.236 & 7.289 \\
\noalign{\smallskip}
\hline
\end{tabular}
\end{table}